Is it possible their test is not very accurate?

The way that we always look for processing speed is in the child's ability to respond almost unbelievably fast, like before you can even finish the question.

Also, once they are taking standardized tests, it is our opinion that the goal was the best accuracy with the fastest speed because the careers that are matched with the highest IQs in one way or another require accuracy with speed.

I do think those tests in school for processing speed are somehow wrong, but I have never observed how they are administered.

If you are comfortable, ask the school for more detail.

Just from your post, it sounds like you are picking up on something for real, so don't ignore it. Their test might be wrong somehow. Good Luck!